Resume - Two tours at same job question

In my job experience I worked for a company and left briefly to work for another company. I ended up back at the first company in the same position though (Second company was a different type of job I did not like so I completed my project and resigned; and it helped that the first made me a big offer to come back).

Should I combine these two tours at the first company into one bullet list?

The problem is most of my accomplishments were completed during my first tour. The second tour I have more responsibilities, but my projects are big and have long schedules. They have not completed so there really are no "results" other than the project is on schedule. But my daily responsibilities have increased the second time. I am not sure how to accurately reflect this fact though.